Middle C in traditional notation is shown below.
It is called middle C as it is in the middle between treble staff and the bass staff.
Middle C frequency
What frequency or pitch is produce by the note middle C depends on the instrument.
On a piano, depending on the tuning, middle C will be approximately 260 Hz (for example, 261.63 Hz in an equal tempered scale in which A above middle C is 440 Hz; see Frequency of notes). On a standard 88 key piano, middle C is also known as C4 and is the C closest to the middle.
The following is middle C on piano.
Click Play to hear middle C on piano.
A guitar plays the same notes on the staff one octave lower. Thus, middle C on a guitar is one octave lower than middle C on a piano. Its frequency is about 130 Hz. On a six-string guitar with standard tuning, this C is played on the third fret of the fifth string.
The following is middle C on guitar.
Click Play to hear middle C on guitar.
Middle C in MIDI
Middle C in MIDI is the C closest to the middle of the notes that a MIDI note on message can produce. The MIDI note on message can produce 128 notes for a specific instrument, denoted in the message by one byte with the decimal values from 0 to 127, and middle C is identified by the value 60.